Crosslinkable fill compositions for uniformly protecting via and contact holes

ABSTRACT

A via and contact hole fill composition and method for using the composition in the dual damascene production of circuits is provided. Broadly, the fill compositions include a quantity of solid components including a polymer binder and a solvent system for the solid components. The boiling point of the solvent system is less than the cross-linking temperature of the composition. Preferred solvents for use in the solvent system include those selected from the group consisting of alcohols, ethers, glycol ethers, amides, ketones, and mixtures thereof. Preferred polymer binders are those having an aliphatic backbone and a molecular weight of less than about 80,000, with polyesters being particularly preferred. In use, the fill composition is applied to the substrate surfaces forming the contact or via holes as well as to the substrate surfaces surrounding the holes, followed by heating to the composition reflow temperature so as to cause the composition to uniformly flow into and cover the hole-forming surfaces and substrate surfaces. The composition is then cured, and the remainder of the dual damascene process is carried out.

RELATED APPLICATION

[0001] This is a continuation of application Ser. No. 09/918,110 filedJul. 30, 2001, which is a continuation of application Ser. No.09/632,823 filed Aug. 7, 2000, now abandoned, which is a continuation ofapplication Ser. No. 09/383,785 filed Aug. 26, 1999, now abandoned, allincorporated by reference herein.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention is broadly concerned with fill compositionsand methods useful for protecting the surfaces forming the contact andvia holes during dual damascene processes for the production ofintegrated circuits. More particularly, the compositions of theinvention comprise a quantity of solid cross-linkable componentsincluding a polymer binder, and a solvent system for the solidcomponents. The boiling point of the solvent system is preferablysufficiently lower than the cross-linking temperature of the compositionso that essentially all of the solvent system is evaporated during thefirst stage bake without the fill composition being cross-linked to anyappreciable degree. In use, the fill compositions are applied to asubstrate previously patterned with contact or via hole according toconventional methods followed by heating the composition to its reflowtemperature in order to evaporate the solvent system and cause thecomposition to flow into the hole for uniform coverage. The compositionis then cured and the remainder of the dual damascene process carriedout in the usual fashion.

[0004] 2. Description of the Prior Art

[0005] The damascene process, or the process of forming inlaid metalpatterning in preformed grooves, is generally a preferred method offabricating interconnections for integrated circuits. In its simplestform, the dual damascene process starts with an insulating layer whichis first formed on a substrate and then planarized. Horizontal trenchesand vertical holes (i.e., the contact and via holes) are then etchedinto the insulating layer corresponding to the required metal linepattern and hole locations, respectively, that will descend down throughthe insulating layer to the device regions (if through the firstinsulating layer, i.e., a contact hole) or to the next metal layer down(if through an upper insulating layer in the substrate structure, i.e.,a via hole). Metal is next deposited over the substrate thereby fillingthe trenches and the holes, and thus forming the metal lines and theinterconnect holes simultaneously. As a final step, the resultingsurface is planarized using the known chemical-mechanical polish (CMP)technique, and readied to accept another dual damascene structure.

[0006] During the dual damascene process, the contact and via holes aretypically etched to completion prior to the trench etching. Thus, thestep of trench etching exposes the bottom and sidewalls (which areformed of the insulating or dielectric layer) of the contact or viaholes to over-etch which can deteriorate the contact with the baselayer. An organic material is therefore used to partially or completelyfill the via or contact holes and to protect the bottom and sidewallsfrom further etch attack. These organic fill materials can also serve asa bottom anti-reflective coating (BARC) to reduce or eliminate patterndegradation and line width variation in the patterning of the trenchlayer, provided the fill material covers the surface of the dielectriclayer.

[0007] Fill materials have been used for the past several years whichhave high optical density at the typical exposure wavelengths. However,these prior art materials have limited fill properties. For example,when the prior art compositions are applied to the via or contact holesformed within the substrate and to the substrate surface, the filmsformed by the compositions tend to be quite thin on the substratesurface immediately adjacent the holes, thus leading to undesirablelight reflection during subsequent exposure steps. Also, because theprior art compositions etch more slowly than the dielectric layer, theunetched fill compositions provide a wall on which the etch polymer willdeposit. This etch polymer build-up then creates undesirable resistancewithin the metal interconnects of the final circuit. These problems areexplained in more detail below.

[0008] There is a need in the art for contact or via hole fill materialswhich provide complete coverage at the top of via and contact holes.Furthermore, this material should provide adequate protection to thebase of the via and contact holes during etching to prevent degradationof the barrier layer and damage to the underlying metal conductors. Inorder to prevent sidewall polymer buildup, the etch rate of the materialshould be equal to or greater than the etch rate of the dielectricmaterial, or the contact or via holes should be filled partially so thatthe fill material in the holes does not extend above the base of thetrench following trench etch.

SUMMARY OF THE INVENTION

[0009] The instant invention overcomes the problems in the art byproviding a fill material or composition which can be applied to viaand/or contact holes during damascene processing to provide completesurface coverage while avoiding undue buildup of the etch polymer aroundthe top edge of the holes at the base of the trench of the damascenestructure.

[0010] In more detail, the compositions (fill material and fillcomposition are used interchangeably herein) of the invention comprise aquantity of solid components including a polymer binder or resin, and asolvent system (either single or multiple solvents) for the solidcomponents. The inventive compositions are superior to prior artcompositions in that they are formulated to achieve two requirements:the inventive composition will freely and evenly flow into the contactor via holes with minimal or no cross-linking of the composition duringthe pre-bake stage (i.e., first stage bake); and during the pre-bakestage essentially all of the solvent is evaporated so that thecomposition incurs very little shrinkage during the final bake stage.These two requirements are quantified by subjecting the composition tothe “pre-bake thermal stability test” and the “film shrinkage test” setforth in detail below.

[0011] There are numerous factors which affect the ability of the fillcomposition to meet the foregoing requirements. For example, the polymerbinder or resin preferably comprises an aliphatic backbone and has amolecular weight of less than about 80,000, preferably less than about25,000, and more preferably from about 2000-7500. Suitable polymerbinders include polyesters, polyacrylates, polyheterocyclics,polyetherketones, polyhydroxystyrene, polycarbonates,polyepichlorohydrin, polyvinyl alcohol, oligomeric resins (such as crownethers, cyclodextrins, epoxy resins), and mixtures of the foregoing. Thesolvent systems utilized in the composition of the invention preferablyhave a boiling point of less than about 160° C., more preferably lessthan about 140° C., and most preferably less than about 120° C. Thesolvent system should also have a flash point of greater than about 85°C., and more preferably greater than about 100° C. When more than onesolvent is utilized in the solvent system, the boiling point or flashpoint of the solvent system refers to the boiling point or flash pointof the highest boiling or lowest flashing solvent. It is also importantthat the solvent system be compatible with the resist system chosen forthe particular damascene process. That is to say, an air-dried film ofthe fill composition should redissolve in the chosen resist solventsystem within 30 seconds with essentially no undissolved residue beingvisible in the solution.

[0012] The concentrations of the solvent system and other volatilespecies present in the composition is not critical, so long as the totalconcentration of the solvent system and volatile species in the filmjust prior to cross-linking of the film (i.e., just prior to the secondstage bake) is less than about 5% by weight, and preferably less thanabout 2% by weight, based upon the total weight of the fill compositiontaken as 100% by weight. This solvent system and volatile weight percentin combination with the above solvent system boiling and flash points isimportant to ensure that minimal shrinking of the composition occursduring the second stage bake. Preferred solvents for use in the solventsystem include alcohols, ethers, glycol ethers, amides, esters, ketones,water, propylene glycol monomethyl ether (PGME), propylene glycolmonomethyl ether acetate (PGMEA), ethyl lactate, and PCBTF(p-chlorobenzotrifluoride), with PGME being particularly preferred.

[0013] The fill compositions of the inventions preferably cross-link ata temperature of from about 150-220° C., and more preferably about 180°C. It is important that the fill compositions cross-link at atemperature higher than the temperature to which the composition isheated during the first stage reflow baking so as to avoid unduecross-linking of the composition during the reflow step. Such prematurecross-linking would prevent the composition from completely anduniformly flowing into the contact or via holes. Cross-linking of thepolymer binder in the composition can be accomplished by the use of across-linking agent in the composition or by the selection of polymerbinders which include “built in” cross-linking moieties. Preferredcross-linking systems include acid or base catalyzed, thermal catalyzed,and photocatalyzed systems such as aminoplasts, epoxides, blockedisocyanates, acrylics, and mixtures thereof.

[0014] All solid components utilized in the fill compositions of theinvention should form a free-flowing liquid at a first stage reflow baketemperature of less than about 200° C., and preferably less than about120° C., thus preventing the composition from adhering to the holesidewalls and forming a steep meniscus. All components must remainchemically stable at these reflow temperatures for at least about 15seconds, and preferably at least about 30 seconds. By chemically stable,it is meant that the components only undergo changes in their physicalstate and not in their chemical state (such as by cross-linking of theircomponents). The chemical stability can be determined by UV/VIS or FTIRanalysis, both before and after the first stage bake.

[0015] In order to avoid the etch polymer buildup problems of the priorart, the etch rate of the fill composition should be approximately equalto the base material or dielectric material etch rate. Furthermore, thefill composition should have a faster etch rate than the etch rate ofthe photoresist. The ratio of the composition etch rate to thephotoresist etch rate should be at least about 1.5:1, preferably atleast about 3:1, and more preferably at least about 4:1. One way toachieve such fill composition etch rates is through the selection of thepolymer binder. Highly oxygenated or halogenated species will result inan increased etch rate.

[0016] The compositions can also be formulated to include optionalingredients as necessary. Optional ingredients include wetting agents(such as fluorinated surfactants, ionic surfactants, non-ionicsurfactants, and surface active polymer additives) and dyes orchromophores. Examples of suitable dyes include any compound thatabsorbs at the electromagnetic wavelength used for the particularprocess. Examples of dyes which can be used include compounds containinganthracene, naphthalene, benzene, chalcone, phthalimides, pamoic acid,acridine, azo compounds, and dibenzofuran. The dyes may be physicallymixed into the composition, or alternately, may be chemically bonded tothe polymer binder. For e-beam exposure, conductive compounds can beused.

[0017] The method of applying the fill compositions to a substrate witha contact or via hole simply comprises applying a quantity of acomposition hereof to the substrate surfaces forming the hole by anyconventional application method (including spin coating). After thecomposition is applied to the hole, it should be heated to its reflowtemperature (as set forth above) during the first stage bake so as tocause the composition to flow into the contact or via hole(s), thusachieving the desired hole and substrate surface coverage. After thedesired coverage is achieved, the resulting fill composition film shouldthen be heated to at least the cross-linking temperature of thecomposition so as to cure the film.

[0018] In partial fill processes, the height of the cured fill materialin the hole should be from about 35-65%, and preferably at least about50% of the depth of the hole. In complete fill processes, the height ofthe cured fill material in the hole should be at least about 95%, andpreferably at least about 100% of the depth of the hole. The height ofthe meniscus of the cured fill composition should be less than about 15%of the depth of the hole, and preferably less than about 10% of the holedepth. Although a meniscus is conventionally deemed to be a concavesurface or “valley” which forms on the top surface of a flowablesubstance in a container (i.e., the via or contact hole), as used hereinthe term meniscus is also intended to include convex surfaces or “hills”formed on the top surface of a substance in a container or hole. Themeniscus height as used herein refers to the distance from the highestpoint at which the composition contacts the sidewalls of the contact orvia holes to the lowest point in the concave surface of the meniscus, orfor a convex meniscus, the distance from the highest point at which thecomposition contacts the sidewalls of the contact or via holes to thehighest point on the convex surface.

[0019] The thickness of the cured fill material film on the surface ofthe substrate adjacent the edge of the contact or via hole should be atleast about 40%, preferably at least about 50%, and more preferably atleast about 70% of the thickness of the film on the substrate surface adistance away from the edge of the contact or via hole approximatelyequal to the diameter of the hole. Finally, the percent of solids in thecompositions should be formulated so that the thickness of the filmformed on the substrate surface is from about 35-250 nm. Following themethods of the invention will yield precursor structures for the dualdamascene process having the foregoing desirable properties.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1A depicts a starting substrate structure for use in apartial fill process using a prior art partial planarizing bottomanti-reflective coating (BARC) as the contact or via hole fill material;

[0021]FIG. 1B depicts the structure of FIG. 1A after a photoresist hasbeen applied to the dielectric layer, exposed, and developed, and thecontact or via hole pattern has been etched;

[0022]FIG. 1C depicts the structure of FIG. 1B after a prior art BARChas been applied to the structure and cured;

[0023]FIG. 1D depicts the structure of FIG. 1C after a photoresist hasbeen applied to the structure, exposed, and developed;

[0024]FIG. 1E depicts the structure of FIG. 1D after the trench patternshave been etched;

[0025]FIG. 1F depicts the structure of FIG. 1E after the photoresist andfill material have been removed from the structure;

[0026]FIG. 1G depicts the structure of FIG. 1F after the barrier layerhas been removed;

[0027]FIG. 1H depicts the structure of FIG. 1G after a metal has beendeposited into the contact or via holes;

[0028]FIG. 1I depicts the final damascene structure formed during thesteps shown in FIGS. 1A-1H;

[0029]FIG. 2A depicts a starting substrate structure for use in acomplete fill process using a prior art planarizing BARC as the contactor via hole fill material;

[0030]FIG. 2B depicts the structure of FIG. 2A after a photoresist hasbeen applied to the dielectric layer, exposed, and developed, and thecontact or via hole pattern has been etched;

[0031]FIG. 2C depicts the structure of FIG. 2B after a prior art BARChas been applied to the structure and cured;

[0032]FIG. 2D depicts the structure of FIG. 2C after a photoresist hasbeen applied to the structure, exposed, and developed;

[0033]FIG. 2E depicts the structure of FIG. 2D after the trench patternshave been etched;

[0034]FIG. 2F depicts the structure of FIG. 2E after the photoresist andfill material have been removed from the structure;

[0035]FIG. 2G depicts the structure of FIG. 2F after the barrier layerhas been removed;

[0036]FIG. 2H depicts the structure of FIG. 2G after a metal has beendeposited into the contact or via holes;

[0037]FIG. 2I depicts the final damascene structure formed during thesteps shown in FIGS. 2A-2H;

[0038]FIG. 3A depicts a starting substrate structure for use in a fillprocess using a prior art conformal type BARC as the contact or via holefill material;

[0039]FIG. 3B depicts the structure of FIG. 3A after a photoresist hasbeen applied to the dielectric layer, exposed, and developed, and thecontact or via hole pattern has been etched;

[0040]FIG. 3C depicts the structure of FIG. 3B after a prior artconformal BARC has been applied to the structure and cured;

[0041]FIG. 3D depicts the structure of FIG. 3C after a photoresist hasbeen applied to the structure, exposed, and developed;

[0042]FIG. 3E depicts the structure of FIG. 3D after the trench patternshave been etched;

[0043]FIG. 3F depicts the structure of FIG. 3E after the photoresist andfill material have been removed from the structure;

[0044]FIG. 3G depicts the structure of FIG. 3F after the remainder ofthe barrier layer has been removed;

[0045]FIG. 3H depicts the structure of FIG. 3G after a metal has beendeposited in the contact or via holes;

[0046]FIG. 3I depicts the final damascene structure formed during thesteps shown in FIGS. 3A-3H;

[0047]FIG. 4A depicts a starting substrate structure for use in acomplete fill process using a fill material of the invention;

[0048]FIG. 4B depicts the structure of FIG. 4A after a photoresist hasbeen applied to the dielectric layer, exposed, and developed, and thecontact or via hole pattern has been etched;

[0049]FIG. 4C depicts the structure of FIG. 4B after a fill materialaccording to the invention has been applied to the structure tocompletely fill the via or contact holes and cured;

[0050]FIG. 4D depicts the structure of FIG. 4C after a photoresist hasbeen applied to the structure, exposed, and developed;

[0051]FIG. 4E depicts the structure of FIG. 4D after the trench patternshave been etched;

[0052]FIG. 4F depicts the structure of FIG. 4E after the photoresist andfill material have been removed from the structure;

[0053]FIG. 4G depicts the structure of FIG. 4F after the barrier layerhas been removed;

[0054]FIG. 4H depicts the structure of FIG. 4G after a metal has beendeposited into the contact or via holes;

[0055]FIG. 4I depicts the final damascene structure formed during thesteps shown in FIGS. 4A-4H;

[0056] IS FIG. 5A depicts a starting substrate structure for use in apartial fill process using a fill material of the invention;

[0057]FIG. 5B depicts the structure of FIG. 5A after a photoresist hasbeen applied to the dielectric layer, exposed, and developed, and thecontact or via hole pattern has been etched;

[0058]FIG. 5C depicts the structure of FIG. 5B after a fill materialaccording to the invention has been applied to the structure topartially fill the contact or via holes and cured;

[0059]FIG. 5D depicts the structure of FIG. 5C after a photoresist hasbeen applied to the structure, exposed, and developed;

[0060]FIG. 5E depicts the structure of FIG. 5D after the trench patternshave been etched;

[0061]FIG. 5F depicts the structure of FIG. 5E after the photoresist andfill material have been removed from the structure;

[0062]FIG. 5G depicts the structure of FIG. 5F after the barrier layerhas been removed;

[0063]FIG. 5H depicts the structure of FIG. 5G after a metal has beendeposited into the contact or via holes;

[0064]FIG. 5I depicts the final damascene structure formed during thesteps shown in FIGS. 5A-5H;

[0065]FIG. 6A depicts a starting substrate structure for use in acomplete fill process using a fill material of the invention followed byapplying a thin BARC over the via/contact fill material;

[0066]FIG. 6B depicts the structure of FIG. 6A after a photoresist hasbeen applied to the dielectric layer, exposed, and developed, and thecontact or via hole pattern has been etched;

[0067]FIG. 6C depicts the structure of FIG. 6B with a fill materialaccording to the invention applied to the structure to completely fillthe contact or via holes and subsequent curing of the fill material,followed by the application of a thin film BARC to the cured fillmaterial and subsequent curing of the thin film;

[0068]FIG. 6D depicts the structure of FIG. 6C after a photoresist hasbeen applied to the structure, exposed, and developed;

[0069]FIG. 6E depicts the structure of FIG. 6D after the trench patternshave been etched;

[0070]FIG. 6F depicts the structure of FIG. 6E after the photoresist,fill material, and thin film BARC have been removed from the structure;

[0071]FIG. 6G depicts the structure of FIG. 6F after the barrier layerhas been removed;

[0072]FIG. 6H depicts the structure of FIG. 6G after a metal has beendeposited into the contact or via holes;

[0073]FIG. 6I depicts the final damascene structure formed during thesteps shown in FIGS. 6A-6H;

[0074]FIG. 7 depicts the meniscus height of a precursor structure in thedual damascene process utilizing a prior art fill composition in acontact or via hole;

[0075]FIG. 8 depicts the meniscus height of a precursor structure in thedual damascene process utilizing a fill composition according to theinstant invention in a contact or via hole;

[0076]FIG. 9 depicts the thickness of a film formed from a prior artfill composition and applied to the surface surrounding a contact or viahole in a precursor structure in the dual damascene process;

[0077]FIG. 10 depicts the thickness of a film formed from the inventivefill composition and applied to the surface surrounding a contact or viahole in a precursor structure in the dual damascene process;

[0078]FIG. 11 is an SEM photograph (50,000X) showing a fill material ofthe invention applied to a via hole and cured;

[0079]FIG. 12 is an SEM photograph (50,000X) showing a fill material ofthe invention applied to a via hole and cured with a thin film ofanti-reflective coating applied to the top of the material followed bycuring of the thin film;

[0080]FIG. 13 is an SEM photograph (50,000X) showing a cured fillmaterial of the invention applied to a via hole according to partial viafill processes;

[0081]FIG. 14 is an SEM photograph (60,000X) showing a prior art BARC ina via hole after curing;

[0082]FIG. 15 is an SEM photograph (50,000X) showing a different priorart BARC material in a via hole after curing; and

[0083]FIG. 16 is an SEM photograph (50,000X) showing a prior art curedBARC partially filling a via hole.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0084] 1. The Problems with Prior Art Processes and Compositions FIGS.1A-1I show various stages of a partial via fill process using prior artorganic fill materials. In FIG. 1A a starting damascene structure 11includes a dielectric material 10 applied to a substrate 12 andinterspersed with a pattern of gate or metal conductors 16. A protectivebarrier layer 18 covers and thus protects dielectric material 10 andconductor 16 during further etching. A dielectric material 20 is appliedimmediately adjacent barrier layer 18. Referring to FIG. 1B, aphotoresist 22 is then applied to the dielectric layer 20 followed byexposure and developing of the resist contact or via hole patterns ontothe dielectric layer 20 and subsequent etching to form the contact orvia holes 24.

[0085] In FIG. 1C, a prior art BARC fill material 26 is applied to holes24 to partially fill the holes to a level of from 35-65% of the originalhole depth followed by curing of the material 26. One notable prior artshortcoming can be seen in FIG. 1C. First, at top edge 28 of the holes24 the BARC material 26 thins and may completely dewet leaving little orno BARC material 26 to prevent reflections which will negatively impactthe trench patterning step as shown in FIG. 1D where the trenchpatterning of a photoresist 30 is degraded at location 32. After thetrench patterning, trenches 34 are etched in the dielectric material 20and part of the dielectric material is eroded between adjacent trenchlines at location 36 (see FIG. 1E) due to the degraded trench pattern.Other problems with the prior art materials is that the cured materialforms a steep meniscus (the meniscus height being represented by “M” inFIG. 1C), and the etch rate of the BARC material 26 is slower than thatof the dielectric layer 20. This slower etch rate combined with thesteep meniscus results in the formation of peaks 38 of the BARC material26 which allow etch polymer 40 to deposit and build up on top of thedielectric layer 20.

[0086] Referring to FIG. 1F, the photoresist 30 and the BARC material 26are then removed from structure 11. However, conventional BARC materialstripping compositions will not remove the polymer 40, and the processesthat do remove the polymer 40 tend to attack the dielectric layer 20and/or protective barrier layer 18. Therefore, the polymer 40 isgenerally left on the structure 11 and the damascene process continued.

[0087] In FIG. 1G, the barrier layer 18 is removed followed by thedeposition of the metal or gate material 42 in the holes 24 and trenches34 (FIG. 1H). After the dual damascene metallization step shown in FIG.1H, conventional CMP processes are carried out, resulting in a completeddamascene structure 44.

[0088] Upon examining structure 44 in FIG. 1I, the problems created bythe above-described prior art fill material shortcomings can be readilyseen. For example, the eroded trench line locations 36 often result in ashort at point 46. Also, the buildup of the etch polymer 40 (which is aninsulating material) leads to higher contact/via resistivities where themetal to metal contact area between the metals in the trenches 34 andthe holes 24 is reduced by the presence of the polymer 40. Furthermore,the buildup of the polymer 40 will cause increased stress in the metalaround the polymer 40, thus occasionally leading to the cracking of themetal around the holes 24 and/or trenches 34 resulting in defects in thefinal circuit.

[0089] FIGS. 2A-2I depict a prior art damascene process very similar tothe process depicted in FIG. 1A-1I except that FIGS. 2A-2I show the“complete” fill (i.e., greater than 95%) of the prior art BARC fillmaterial 26 in the contact or via holes 24 as shown in FIG. 2C. The useof the complete fill process eliminates the thinning problem asdiscussed above with respect to the top edge 28 of the holes 24 in FIG.1C. However, the slower etch rate of the BARC material 26 still causesthe buildup of the etch polymer 40 as shown in FIGS. 2E-2I. Again, thisleads to higher resistivities and metal stress around the polymerbuildup.

[0090] FIGS. 3A-3I illustrate a prior art process for forming damascenestructures which is very similar to the processes discussed above exceptthat the prior art BARC fill material 26 is applied to the via orcontact holes 24 in what is known as a “conformal” fashion. Referring toFIG. 3C, the conformal application is illustrated wherein a thin film ofthe BARC material 26 is coated over top surface 48 of the dielectriclayer 20, down edge surfaces 50 of the holes 24, and on bottom surfaces52 of the holes 24. When conformally applied, the BARC material 26maintains nearly uniform thickness, providing good reflectivity controland minimizing damage to the trench pattern integrity. However, theslower etch rate of the BARC material 26 again leads to the problem ofthe etch polymer 40 building up on the dielectric layer 20 as shown inFIGS. 3E-3I.

[0091] Another problem with using prior art BARC materials in aconformal fashion is that the bottom surfaces 52 of the holes 24 oftendo not have sufficient protection from the etch gas during the etchingprocess. Referring to FIG. 3E, the barrier layer 18 can be breachedduring etching, thus exposing the conductors 16 to attack. The etch gasutilized during the trench etching process or the resist strip removalprocess may also attack the conductors 16 as shown in FIG. 3F. Theresist strip process generally consists of several steps including:oxygen plasma strip, ozone plasma strip, and various wet chemistriessuch as ozonated water, sulfuric peroxide, hydrogen peroxide, and diluteHF followed by water rinses. For most metal conductors 16, the wetchemistries will directly etch the metal and cause metal corrosionduring the following rinse step, absent the protective barrier layer 18.The oxygen radical-based plasma strip process can also form stable metaloxides on the surface of the metal, thus degrading the via or contactreliability. This in turn will lead to high via or contact resistanceand/or complete failure of the interconnect at point 54 (FIG. 3I) aftervia or contact dual damascene metallization.

[0092] 2. The Present Invention

[0093] FIGS. 4A-4I, 5A-5I, and 6A-6I illustrate the improved damascenestructures that can be obtained utilizing fill materials formulatedaccording to the instant invention. FIGS. 4A-4I show a complete via fillprocess using organic fill materials having the properties describedabove. In FIG. 4A, a starting damascene structure 56 includes adielectric material 58 applied to a substrate 60 and interspersed with apattern of gate or metal conductors 64 (formed of aluminum, copper,tungsten, or other conducting material). The substrate 60 can be formedof silicon, GaAs, or other semiconductor materials with regions ofdoping to provide source and drain areas or any other electricalelement. A protective barrier layer 66 covers and thus protects thedielectric material 58 and conductors 64 during further etching steps.The barrier layer 66 can be formed of silicon, tantalum, and titaniumnitrides, as well as titanium and tantalum oxides. A dielectric layer 68is applied immediately adjacent the barrier layer 66. The dielectricmaterial 58 and the dielectric material 68 may be formed of mostinsulating materials, including silicon dioxide, silicon nitrides,fluorinated oxides, and titanium oxides. Referring to FIG. 4B, aphotoresist 70 is applied to the dielectric layer 68 followed byexposure and developing of the contact or via hole pattern onto thedielectric layer 68 and subsequent etching to form the contact or viaholes 72.

[0094] In FIG. 4C, a BARC fill material 74 formulated according to theinstant invention is applied to the holes 72, preferably by the spincoat or spray coat methods, to essentially completely (i.e., at least95% of the holes' depth) fill the holes 72 . The material 74 is thencured by heating to its cross-linking temperature. During the depositionof material 74, the substrate to which the material 74 is applied may bestatic, or it may be spinning with a rotation of from about 200-5000rpm. The material 74 can be applied in either a radial or reverse radialmanner. Alternately, the material 74 can be applied by a sprayatomization method. If necessary, in order to improve via or contactfill depth, a second or third fill composition layer can be appliedafter spinning the previous coat for about 15-60 seconds at a rotationalspeed of at least about 1500 rpm. Finally, the material 74 can also beapplied utilizing the spike spin method wherein the material 74 isapplied to the substrate while the substrate is accelerated to arotational speed of about 3000-7000 rpm for about 1-3 seconds followedby deceleration to a rotational speed of from about 200-3000 rpm andspun until dry. After the application of one or more coats of the via orcontact fill composition and spin drying to remove the solvent(s), thefilm of material 74 is ready to bake.

[0095] The initial bake step (or first stage bake) removes the volatilebyproducts and solvent systems from the fill composition film and heatsthe film to a temperature above the reflow point of the combined solidcomponents present in the material 74. When heated to the reflow point,the material 74 will liquify and readily flow into the via or contactholes 72 under the force of gravity, capillary forces, or surfacewetting dynamic forces to provide the desired coverage and hole filllevels and to displace trapped air, solvents, and volatiles evolvingfrom the material 74. The initial bake temperature should be less thanabout 200° C., preferably less than about 140° C., and more preferablyless than about 120° C. The initial bake step should not result in achemical change in the liquified fill material 74 (e.g., the materialshould not cross-link). The initial bake step may be carried out in anynumber of ways including but not limited to a contact hotplate, aproximity hotplate with a gas pillow between the substrate and hotplatesurface, a proximity hotplate with proximity pins between the substrateand the hotplate surface, convection oven, infrared oven, or halogenrapid thermal processing oven. Upon being liquified during the initialbake step, the material 74 will reach the desired coverage in less thanabout 60 seconds, preferably less than about 15 seconds, and morepreferably less than about 1 second.

[0096] Once the material 74 has flowed sufficiently to achieve thedesired coverage, the material 74 is cured in a second stage bake. Thesecond stage bake cross-links the film of the material 74 to prevent thematerial 74 from interfering with subsequent resist coating andprocessing. Once the material 74 is cured, a photoresist 76 is applied,exposed, and developed to form patterns for trenches 78 which aresubsequently etched. Because the material 74 has an etch rate equal toor greater than the etch rate of the dielectric layer 68, the problem ofetch polymer buildup on the layer 68 prevalent in the prior art iseliminated as can be seen in FIGS. 4E-4I.

[0097] Referring to FIG. 4F, the photoresist 76 and the BARC material 74are removed from structure 56 without damage to the barrier layer 66.This is typically accomplished by plasma etch, ozone strip, ozonatedwater strip, organic solvent strip, sulfuric peroxide cleaning, hydrogenperoxide cleaning or any combinations of the foregoing strip and cleanprocesses. In FIG. 4G, the barrier layer 66 is then removed (such as byplasma etch) followed by the deposition of a metal or gate material 80(with appropriate barrier and seed layers, if necessary) in the holes 72and trenches 78 (FIG. 4H). After the dual damascene metallization stepshown in FIG. 4H, conventional CMP processes are carried out resultingin a completed damascene structure 82. Unlike the prior art, theresulting structure 82 is formed without any via or contact hole fillresidues, sidewall polymer buildup or crowns around the top of the viaor contact holes, or pattern distortions leading to shorting of adjacenttrenches.

[0098] The process shown in FIGS. 5A-5I is similar to the processdescribed above with respect to FIGS. 4A-4I except that FIGS. 5A-5Iillustrate the partial fill process utilizing fill materials accordingto the instant invention. FIGS. 6A-6I depict an alternate embodimentwherein a thin film of a BARC 84 is spin coat-applied over the curedfill material 74, followed by curing of the BARC film. The film 84 canbe tailored to the electromagnetic wavelength used for subsequent resistexposure. The second film protects the subsequent resist pattern fromelectromagnetic wave variations which lead to a degraded resist pattern.Alternately, a conductive film for e-beam exposure can be applied inplace of the film 84 to reduce the impact of charging within thesubstrate which would cause degradation of the e-beam resist pattern. Aresist film 76 is then applied and patterned as described previously.

[0099] FIGS. 7-10 compare damascene structures utilizing fillcompositions according to the invention to structures utilizing priorart fill compositions. In FIG. 8, the meniscus formed by a fillcomposition 86 formulated according to the instant invention and appliedto a via or contact hole 88 is much less steep than the meniscus formedby a prior art fill material 90 applied to a via or contact hole 92 andshown in FIG. 7. Thus, relative to the height H of the via or contacthole, the fill compositions of the instant invention have a meniscusheight M of less than about 15% of H, and preferably less than about 10%of H. For example, if the height H of a via hole was 200 nm, themeniscus height M should be less than about 30 nm, and preferably lessthan about 20 nm. This meniscus height M in combination with the etchrate of the fill composition prevents the polymer buildup problems ofthe prior art, thus yielding metal conductors within the contact or viaholes without increased resistance.

[0100]FIG. 9 shows the thickness of the prior art film 90 on a surface94 of a dielectric material 96 adjacent a via or contact hole opening98. FIG. 10 illustrates the thickness of an inventive film 100 on asurface 102 of a dielectric material 104 adjacent a via or contact holeopening 106. In both FIGS. 9 and 10, the respective films 90, 100 have athickness “T” at a distance from the edge of the hole approximatelyequal to the diameter of the hole. Each film also has a thickness “t” atareas on or closely adjacent the hole edge. The thickness t of theinventive film 100 is greater than the thickness t of the prior artprior art film 90. When using the inventive fill compositions in thedual damascene processes, t should be at least about 40% of T,preferably at least about 50% of T, and more preferably at least about70% of T. For example, if a given hole has a diameter of 200 nm, then atabout that distance from the edge of the hole, t should be at leastabout 0.4T.

Composition Testing

[0101] In order to determine whether a particular composition meets therequirements of the invention, the composition is subjected to thefollowing tests:

[0102] 1. Pre-Bake Thermal Stability Testing

[0103] The fill material should be reflowable and densified during thepre-bake step in order to achieve the desired fill level and fillprofile. To accomplish this, the substrate and fill material must beheated to a temperature that will remove the casting solvent from thefilm and allow the film to flow and densify prior to cross-linking ofthe fill material. With the onset of cross-linking, the film viscosityand flow point increase as the film's solubility in the solventdecreases and the chemical links become rigid, thus reducing thepotential density of the film.

[0104] As used herein, a “pre-bake thermal stability test” determinesthe degree of cross-linking during the pre-bake stage and is conductedas follows. The via fill material is spin-coated onto a flat siliconwafer followed by a 30 second pre-bake at a temperature that is either:the standard pre-bake temperature recommended by the manufacturer of theparticular prior art fill material; or, above the boiling point of allsolvents present in the inventive fill material. Following the pre-bake,the film thickness is measured with an ellipsometer and recorded. Asolution of a casting solvent or solvents (selected for the particularfill composition being tested) is then applied to the surface of thewafer for 5 seconds followed by spin drying at 5000 rpm for 30 seconds.Finally, the sample is baked at 100° C. for 30 seconds, and the filmthickness is measured again to determine the percent of the fillmaterial removed by the casting solvent. The percent of material removedcorresponds to the quantity of noncross-linked fill composition. Theinventive fill compositions are at least about 70% removed, preferablyat least about 85% removed, and more preferably essentially completelyremoved during this test.

[0105] 2. Final Bake Film Solvent Resistance Testing

[0106] In order for a fill material to perform properly as a sublayerfor a photoresist layer, the cured fill material must be relativelyinsoluble in the solvent system from which the particular photoresist iscast. This is necessary to avoid the mixing of the fill material withthe photoresist which typically degrades the performance of thephotoresist. As used herein, to determine whether a particular curedfill material is insoluble in the preferred resist solvent system, a“final bake film solvent resistance test” is conducted as follows. Thevia fill material is spin-coated onto a flat silicon wafer followed by apre-bake for 30 seconds at a temperature that is either: the standardpre-bake temperature recommended by the manufacturer of the particularprior art fill material; or above the boiling point of all solventspresent in the inventive fill material. The sample is then subjected toa final bake for 60-90 seconds at a temperature above the material'scross-linking temperature. After the final bake, the film thickness ismeasured (with an ellipsometer) and recorded. PGME is applied to thesurface of the wafer for 5 seconds followed by spin-drying at 5,000 rpmfor 30 seconds and a 30 second bake at 100° C. The film thickness ismeasured again. The final film should remain intact with little loss orincrease in thickness. Thus, the film thickness after the solventcontact should change less than about ±3%.

[0107] 3. Film Shrinkage Testing

[0108] To obtain the desired fill material profile in a via or contacthole, the shrinkage of the fill material film between the pre-bake andfinal bake should be minimal. As used herein, a “film shrinkage test” isconducted as follows. The fill material is spin-coated onto a siliconwafer followed by a 30 second pre-bake at a temperature that is either:the standard pre-bake temperature recommended by the manufacturer of theparticular prior art fill material; or above the boiling point of allsolvents present in the inventive fill material. After the pre-bake, thefilm thickness is measured (with an ellipsometer) and recorded. Thecoated wafer is then subjected to a final bake at a temperature that isat least the cross-linking temperature of the material, after which thefilm thickness is determined. The percent shrinkage is calculated asfollows:

[0109] % shrinkage=[(pre-bake thickness—final thickness)/pre-bakethickness]×100

[0110] The inventive fill compositions have less than about 15%shrinkage, and preferably less than about 10% shrinkage during thistest.

EXAMPLES

[0111] The following examples set forth preferred methods in accordancewith the invention. It is to be understood, however, that these examplesare provided by way of illustration and nothing therein should be takenas a limitation upon the overall scope of the invention.

Example 1

[0112] 1. Copolymer Syntheses

[0113] Using a mantle for heating, the instant reaction was carried outin a three liter, 4-necked flask equipped with a mechanical stirringrod, thermometer, nitrogen inlet plus thermocouple, and a condenserhaving a nitrogen outlet. Under ambient conditions, the followingcompounds were charged: 13.59 g of glycidyl methacrylate; 25.25 g ofhydroxyl propyl methacrylate; 1.17 g of 2,2′-azobisisobutyronitrile; and1.17 g of 1-dodecanethiol in 158.83 g of PGME. The resulting solutionwas stirred under nitrogen for 15 minutes to remove oxygen, followed bystirring under nitrogen for 24 hours at 70° C. The heat and nitrogenwere turned off, and the reaction mixture was allowed to cool to roomtemperature.

[0114] 2. Mother Liquor Syntheses

[0115] Using a mantle for heating, the instant reaction was carried outin a three liter, 4-necked flask equipped with a mechanical stirringrod, thermometer, nitrogen inlet plus thermocouple, and a condenserhaving a nitrogen outlet. Under ambient conditions, the followingcompounds were charged: 65 g of the copolymer prepared in Part 1 of thisexample (20 weight % in PGME); 6.85 g of 9-anthracenecarboxylic acid;0.173 g of benzyltriethylammonium chloride; and 27.75 g of PGME. Thereaction mixture was then refluxed under nitrogen for 24 hours, afterwhich the heat was turned off and the nitrogen disconnected, allowingthe mixture to cool to room temperature.

Example 2 Preparation of Full Fill Via or Contact Fill Material

[0116] A via or contact fill material was prepared by mixing 27.62% byweight of the mother liquor prepared in Part 2 of Example 1 with 1.73%by weight Cymel 303LF (cross-linking material available from CytechIndustries, Inc.), 27.35% of PGMEA, and 43.3% by weight of PGME. Themixture was stirred for about 1 hour to give a clear solution afterwhich it was exchanged for 15 hours with 7.24% (based on the weight ofthe mixture) of 650C. exchange resin. The resulting mixture was thenfiltered through 2×0.1 μm (absolute) end-point filters. This materialwas coated onto two silicon wafers at a spin speed of 2500 rpm for 60seconds followed by baking at 160° C. for 1 minute and then a 215° C.bake for 90 seconds. The resulting film had a thickness of approximately1560 Å.

[0117] This composition was then applied by spin coating to two siliconwafers. The via fill material was static applied then ramped with anacceleration of 20,000 rpm/second to 2500 rpm and held for 60 seconds.The wafers were pre-baked at 160° C. for 60 seconds in contact hotplatemode. Wafer 1 had a film thickness of 1701 Å and wafer 2 had a filmthickness of 1702 Å.

[0118] The pre-bake thermal stability test set forth in the testingsection above was conducted on wafer 1. The film thickness afterstripping was 0 Å. Thus, the film remained completely soluble at thepre-bake stage, indicating that essentially no cross-linking hadoccurred. Wafer 2 was then baked at 215° C. for 90 seconds in contacthotplate mode. The resulting film thickness was 1561 Å, a decrease of141 Å (a shrinkage of 8.3%). Finally, wafer 2 was subjected to the finalbake film solvent resistance test described previously. The post-stripthickness was 1,563 Å, an increase of 2 Å or 0.13%. Thus, thiscomposition met the minimum film requirements of the fill composition ofthe invention.

Example 3 Preparation of Partial Fill Via or Contact Fill Material

[0119] The material prepared above in Example 2 was diluted with PGMEand PGMEA to produce a via or contact fill material which would providea film of about 550-600 Å. This fill material was applied to two siliconwafers at a spin speed of 2500 rpm for 60 seconds, followed by a 160° C.bake for 1 minute and a 215° C. bake for 60 seconds to form a filmhaving a thickness of about 590 Å, confirming that the material wasproperly diluted.

[0120] The diluted fill material was then spin-coated onto two siliconwafers with static application followed by an acceleration of 20,000rpm/second to 2500 rpm which was held for 60 seconds. Both wafers werepre-baked at 160° C. for 60 seconds in contact hotplate mode. Thethicknesses of the films on wafers 1 and 2 were 639 Å and 644 Å,respectively. The pre-bake thermal stability test was conducted on wafer1. The film thickness after stripping was 0 Å. The film remainedcompletely soluble after the prebake, indicating that essentially nocross-linking had occurred. Wafer 2 was then baked at 215° C. for 60seconds in contact hotplate mode. The resulting film thickness was 593Å, a decrease of 51 Å which corresponds to a 7.9% film shrinkage.Finally, wafer 2 was subjected to the final bake film solvent resistancetest, resulting in a post-strip thickness of 587 Å, a loss of 6 Å (or1%) after the final bake. Thus, the fill material met the minimumrequirements.

Example 4 Full Fill Via or Contact Fill Applications

[0121] The composition prepared in Example 2 was coated over an oxidefilm with 1 μm deep, 0.35 μm diameter holes patterned on a siliconwafer. The composition was coated by dynamic dispensing on the substrateat a 400 rpm spin speed held for 5 seconds, followed by a 20,000rpm/second acceleration to the final spin speed of 1500 rpm which washeld for 30 seconds. The film was then pre-baked in contact hotplatemode at 160° C. for 60 seconds followed by a contact hotplate final bakeat 215° C. for 60 seconds. The wafer was then cross-sectioned for SEManalysis (50,000X) of the fill composition profile in the hole (see FIG.11). The fill material completely filled the hole, and had a thicknessof 104 nm at the top edge of the hole and 113 nm approximately 350 nmaway from the edge of the hole. The meniscus height M was about 66 nm.

[0122] Thus, the fill material completely filled the hole as is requiredin full via or contact hole fill applications. The difference in filllevels between the edge of the hole and the center of the hole should beless than about 15% of the original hole depth. In this case thedifference was less than 6.6%. The film thickness of the fillcomposition at the edge of the hole should be at least about 40% of thefilm thickness at a distance from the edge of the hole about equal tothe diameter of the hole. In this example, the film thickness at thehole edge was 92% of the thickness one hole diameter of (i.e., 350 nm)away from the hole edge. Thus, this composition met the specifications.

Example 5 Full Fill Via or Contact Fill Material With Second Layer of aThin Anti-reflective Coating

[0123] The steps of Example 4 were repeated using a thin,industry-standard anti-reflective coating (DUV30-6 ARC® which providesapproximately a 600 Å thick film on flat silicon when used according tomanufacturer's specifications, available from Brewer Science, Inc.,Rolla, Mo.) was applied over the via fill material. The DUV30-6 wasapplied by dynamic dispensing on the cured via fill material at a spinspeed of 400 rpm held for 5 seconds, followed by an acceleration of20,000 rpm/second to a final spin speed of 3000 rpms which was held for30 seconds. The film was then given a contact hotplate pre-bake at 100°C. for 30 seconds followed by a contact hotplate final bake of 175° C.for 60 seconds. The wafer was then cross-sectioned for SEM analysis(50,000X) to examine the fill composition profile in the hole (see FIG.12). The fill material completely filled the hole as required. Thethickness of the film at the top edge of the hole was 150 nm, while thethickness of the film approximately 350 nm from the edge of the hole was150 nm. The meniscus height M was 31 nm. The difference between the filldepth at the edge of the hole and the fill depth at the center of thehole was 3.1% of the original hole depth. The thickness of the film 350nm away from the hole was the same as the thickness at the edge of thehole, meeting all of the requirements for the film.

Example 6 Partial Fill Via or Contact Fill Applications

[0124] The composition prepared in Example 3 was coated over an oxidefilm with 1 μm deep, 0.35 μm diameter holes patterned on a siliconwafer. The composition was coated by dynamic dispensing on the substrateat a 400 rpm spin speed held for 5 seconds, followed by a 20,000rpm/second acceleration to the final spin speed of 1500 rpm which washeld for 30 seconds. The film was then pre-baked in contact hotplatemode at 160° C. for 60 seconds followed by a contact hotplate final bakeat 215° C. for 60 seconds. The wafer was cross-sectioned for SEManalysis (50,000X) of the fill composition profile in the hole (see FIG.13). The fill material filled the hole to 535 nm, and had a thickness of38 nm at the top edge of the hole and 59 nm approximately 350 nm awayfrom the edge of the hole. The meniscus height M was about 129 nm.

[0125] In partial via or contact hole fill applications, the fillmaterial should fill the hole to between 35% and 65% of the hole depth.In this example, the hole was filled to 53%. The difference in filllevels between the edge of the hole and the center of the hole was12.9%. The film thickness of the fill composition at the edge of thehole was 64.4% of the thickness 350 nm away from the hole. Thus, thiscomposition met the specifications.

Example 7 Full Fill Via or Contact Fill Applications With A Prior ArtBARC

[0126] A prior art BARC (DUV30-16) was utilized to demonstrate theperformance of prior art compositions. The DUV30-16 was applied to twosilicon wafers by dynamic dispensing on the wafers at a spin speed of400 rpm which was held for 5 seconds, followed by an acceleration of20,000 rpm/second to a final spin speed of 1500 rpm which was held for30 seconds. Both wafers were subjected to a 100° C. pre-bake in contacthotplate mode for 30 seconds. The film thicknesses on wafers 1 and 2were 1710 Å and 1758 Å, respectively. The pre-bake thermal stabilitytest was conducted on wafer 1, with the post-strip thickness being 1484Å. The film was substantially insoluble after the pre-bake, indicatingthat significant cross-linking had occurred.

[0127] Wafer 2 was then baked at 175° C. for 60 seconds in contacthotplate mode. The resulting film thickness was 1605 Å, a decrease of153 Å which corresponds to a film shrinkage of 8.7%. Wafer 2 was thensubjected to the final bake film solvent resistance test. The post-stripthickness of wafer 2 was 1610 Å, an increase of 5 Å (or a shrinkage of−0.31%) after the final bake. Thus, the prior art BARC passed the finalbake solvent resistance test and the film shrinkage test. However, theprior art BARC failed the prebake stability test in that only 13.2% ofthe fill composition was removed by the solvent after the pre-bake,which is substantially below the minimum requirement of at least about70% removal.

[0128] The DUV30-16 was coated over an oxide film with 1 μm deep, 0.35μm diameter holes patterned on a silicon wafer. The composition wascoated by dynamic dispensing on the substrate at a 400 rpm spin speedheld for 5 seconds, followed by a 20,000 rpm/second acceleration to thefinal spin speed of 1500 rpm which was held for 30 seconds. The film wasthen pre-baked in contact hotplate mode at 100° C. for 30 secondsfollowed by a contact hotplate final bake at 175° C. for 60 seconds. Thewafer was cross-sectioned for SEM analysis (60,000X) of the fillcomposition profile in the hole (see FIG. 14). The fill material did notcompletely fill the hole, but instead only had a fill height of 908 nm.The film thickness was 93 nm at the top edge of the hole and 157 nmapproximately 350 nm away from the edge of the hole. The meniscus heightM was about 220 nm.

[0129] Thus, the fill material only filled the hole to 93% of the holedepth rather than to at least about 95% as is required in full via orcontact hole fill applications. Also, the difference in fill levelsbetween the edge of the hole and the center of the hole (i.e., themeniscus height M) should be less than about 15% of the original holedepth. In this case the difference was 22%, which is greater than theallowable 15% meniscus height M. The film thickness of the fillcomposition at the edge of the hole should be at least about 40% of thefilm thickness at a distance from the edge of the hole about equal tothe diameter of the hole. In this example, the film thickness at thehole edge was 59.5% of the thickness one hole diameter (i.e., 350 nm)away from the hole edge. Thus, this composition met this latterspecification.

[0130] In sum, the film substantially cross-linked during the pre-bakestep and did not achieve the full fill requirements for full fillapplication, resulting in a meniscus height M in excess of the maximumallowable height.

Example 8 Full Fill Via or Contact Fill Material Applications With aPrior Art BARC

[0131] A prior art BARC (EXP97053, available from Brewer Science, Inc.)was utilized to demonstrate the performance of prior art compositions.The EXP97053 was applied to two silicon wafers by dynamic dispensing onthe wafers at a spin speed of 400 rpm which was held for 5 seconds,followed by an acceleration of 20,000 rpm/second to a final spin speedof 2500 rpm which was held for 30 seconds. Both wafers were subjected toa 100° C. pre-bake in contact hotplate mode for 30 seconds. The filmthicknesses on wafers 1 and 2 were 2281 Å and 2272 Å, respectively. Thepre-bake thermal stability test was conducted on wafer 1, with thepost-strip thickness being 138 Å. Thus, the film remained mostly solubleafter the pre-bake, indicating that a small amount of cross-linking hadoccurred.

[0132] Wafer 2 was then baked at 175° C. for 60 seconds in contacthotplate mode. The resulting film thickness was 1888 Å, a decrease of384 Å which corresponds to a film shrinkage of 16.9%. Wafer 2 was thensubjected to the final bake film solvent resistance test. The post-stripthickness of wafer 2 was 1877 Å, a loss of 11 Å (or a shrinkage of 0.6%)after the final bake. Thus, the prior art BARC passed the final bakesolvent resistance test and the pre-bake thermal stability test.However, the prior art BARC failed the film shrinkage test in that thefilm thickness decreased by 16.9% during the final bake.

[0133] The EXP97053 was coated over an oxide film with 1 μm deep, 0.35μm diameter holes patterned on a silicon wafer. The composition wascoated by dynamic dispensing on the substrate at a 400 rpm spin speedheld for 5 seconds, followed by a 20,000 rpm/second acceleration to afinal spin speed of 2500 rpm which was held for 30 seconds. The film wasthen pre-baked in contact hotplate mode at 100° C. for 30 secondsfollowed by a contact hotplate final bake at 175° C. for 60 seconds. Thewafer was cross-sectioned for SEM analysis (50,000X) of the fillcomposition profile in the hole (see FIG. 15). The fill material did notcompletely fill the hole, but instead only had a fill height of 745 nm.The film thickness was 102 nm at the top edge of the hole and 124 nmapproximately 350 nm away from the edge of the hole. The meniscus heightM was about 412 nm.

[0134] The fill material only filled the hole to 74.5% of the hole depthrather than to at least about 95% as is required in full via or contacthole fill applications. The difference in fill levels between the edgeof the hole and the center of the hole was 41.2%, which is greater thanthe allowable 15% meniscus height M. The film thickness of the fillcomposition at the edge of the hole was 82.3% of the thickness one holediameter of (i.e., 350 nm) away from the hole edge. Thus, thiscomposition meets the latter specification.

[0135] In sum, the film did not achieve all of the full fillrequirements for full fill applications. Rather, the film had a largeamount of shrinkage between the pre-bake and final bake, leading to alarge meniscus height M and an inability to fully fill the hole.

Example 9 Partial Fill Via or Contact Fill Material Applications With aPrior Art BARC

[0136] A prior art BARC (EXP97053, which was formulated to provide anapproximately 800 Å thick film) was utilized to demonstrate theperformance of prior art compositions. The EXP97053 was applied to twosilicon wafers by dynamic dispensing on the wafers at a spin speed of400 rpm which was held for 5 seconds, followed by an acceleration of20,000 rpm/second to a final spin speed of 2500 rpm which was held for60 seconds. Both wafers were subjected to a 100° C. pre-bake in contacthotplate mode for 30 seconds. The film thicknesses on wafers 1 and 2were 799 Å and 805 Å, respectively. The pre-bake thermal stability testwas conducted on wafer 1, with the post-strip thickness being 345 Å. Thefilm remained partially soluble after the pre-bake, indicating that somecross-linking had occurred with a stripping of 56.8%. Wafer 2 was thenbaked at 175° C. for 60 seconds in contact hotplate mode. The resultingfilm thickness was 662 Å, a decrease of 143 Å which corresponds to afilm shrinkage of 17.8%. Wafer 2 was subjected to the final bake filmsolvent resistance test. The post-strip thickness of wafer 2 was 657 Å,a loss of 5 Å (or a shrinkage of 0.7%) after the final bake. Thus, theprior art BARC passed the final bake solvent resistance test. However,the prior art BARC failed the film shrinkage test in that the filmthickness decreased by 17.8% during the final bake. The prior art BARCalso failed the pre-bake thermal stability test in that only 56.8% ofthe fill composition was removed.

[0137] The EXP97053 was coated over an oxide film with 1 μm deep, 0.35μm diameter holes patterned on a silicon wafer. The composition wascoated by dynamic dispensing on the substrate at a 400 rpm spin speedheld for 5 seconds, followed by a 20,000 rpm/second acceleration to thefinal spin speed of 2500 rpm which was held for 30 seconds. The film wasthen pre-baked in contact hotplate mode at 100° C. for 30 secondsfollowed by a contact hotplate final bake at 175° C. for 60 seconds. Thewafer was then cross-sectioned for SEM analysis (50,000X) of the fillcomposition profile in the hole (see FIG. 16). The fill material filledthe hole to 426 nm, with the thickness of the film being 14 nm at thetop edge of the hole and 32 nm approximately 350 nm away from the edgeof the hole. The meniscus height M was about 257 nm.

[0138] In partial fill applications, the material should fill the holeto between 35% and 65%. In this example, the material filled the hole to42.6%. The difference in fill levels between the edge of the hole andthe center of the hole was 25.7%, which is greater than the allowable15% meniscus height M. The film thickness of the fill composition at theedge of the hole was 43.8% of the thickness one hole diameter of (i.e.,350 nm) away from the hole edge, just meeting this requirement.

[0139] In sum, this composition had significant cross-linking and alarge amount of shrinkage between pre-bake and final bake (leading to alarge meniscus) and did not meet the minimum requirements.

We claim:
 1. In a fill composition for coating contact or via holesformed in a base material to protect the base material during etchingprocesses, the composition including a quantity of solid componentsincluding a polymer binder, and a solvent system for said solidcomponents, the improvement which comprises: said composition being atleast about 70% removed from the base material when subjected to apre-bake thermal stability test; and said composition having less thanabout 15% shrinkage when subjected to a film shrinkage test.
 2. Thecomposition of claim 1, said solvent system boiling point being lessthan about 160° C.
 3. The composition of claim 1, said solvent systemhaving a flash point of greater than about 85° C.
 4. The composition ofclaim 1, wherein said polymer binder has a molecular weight of less thanabout 80,000.
 5. The composition of claim 1, wherein said polymer bindercomprises polyacrylate.
 6. The composition of claim 1, wherein saidsolvent system includes a solvent selected from the group consisting ofalcohols, ethers, glycol ethers, amides, esters, ketones, and mixturesthereof.
 7. The composition of claim 6, wherein said solvent is PGME. 8.The composition of claim 1, wherein said composition includes across-linking agent.
 9. The composition of claim 8, wherein saidcross-linking agent is selected from the group consisting ofaminoplasts, epoxides, isocyanates, acrylics, and mixtures thereof. 10.The composition of claim 1, wherein said polymer binder includes across-linking moiety.
 11. The composition of claim 8, wherein thecross-linking temperature of said composition is from about 150-220° C.12. The composition of claim 1, wherein said solid components, whenmixed together, have a melting point of less than about 200° C.
 13. Thecomposition of claim 1, said composition and said base material eachhaving respective etch rates, said composition etch rate beingapproximately equal to said base material etch rate.
 14. The compositionof claim 1, said composition further including a light-absorbing dye.15. The composition of claim 14, wherein said dye is bonded to saidpolymer binder.
 16. The composition of claim 1, said composition furtherincluding a wetting agent.
 17. The composition of claim 16, wherein saidwetting agent is a fluorinated surfactant.